Implement policy parameter for % of poverty line below which gross monthly income must be for SNAP

[MaxGhenis]

Currently 1.3 (130%) per https://www.cbpp.org/research/food-assistance/a-quick-guide-to-snap-eligibility-and-benefits

Gross monthly income — that is, household income before any of the program’s deductions are applied — generally must be at or below 130 percent of the poverty line. For a family of three, the poverty line used to calculate SNAP benefits in federal fiscal year 2021 is $1,810 a month. Thus, 130 percent of the poverty line for a three-person family is $2,353 a month, or about $28,200 a year. The poverty level is higher for bigger families and lower for smaller families